Several million women experience debilitating physical and psychological symptoms during the early menopausal transition (EMT) each year. Self-reported sleep disturbance is an almost ubiquitous phenomenon in symptomatic women, and contributes to the economic and social costs of reduced productivity and increased load to the health care system from treatment seeking behavior. Previous studies have failed to find underlying mechanisms for this perceived sleep disturbance. We hypothesize that women who develop symptoms in association with reproductive hormone changes during the EMT have altered central or autonomic nervous system (ANS) regulation that can disrupt the restorative function of sleep. We also hypothesize that regulation of the ANS in these women varies over the menstrual cycle. We aim to test these hypotheses in Specific Aims 1 and 2 using sensitive measures of electroencephalographic (EEG) and ANS activity during sleep. Symptomatic women also consistently report higher levels of stress, exposure to which will often exacerbate menopausal symptoms. Stress is also a common precipitant of sleep disturbance via its impact on the ANS. Specific Aim 3 will test the hypothesis that symptomatic women in the EMT will show altered reactivity of the ANS during sleep following exposure to an acute stressor. These studies provide a novel approach to investigating the mechanisms underlying sleep disturbance commonly experienced in the menopausal years. The study will also provide information as to stress reactivity in symptomatic women and inform the mechanisms underlying their observed elevated risk of cardiovascular morbidity.